Material handling or cargo slings have been in existence for many years. In principle the slings have been of a belt type where at each end there are provided handles having openings therein whereby the handles may be placed on a hook of a hoist once the material or cargo has been girdled by the belt and the material may then be lifted for movement. In some cases the belts terminate in the necessary hoist openings thereby eliminating the specific need for handles per se.
The most generally used slings have been fabricated from single to multiple strands of chain or wire rope lengths. Additionally, some slings are formed of fabric or synthetic material, particularly where a wide area of belting is necessary to engage material or cargo.
The aforementioned slings each has disadvantages which render them unsuitable for certain applications and additionally require high maintenance. As an illustration, when a single strand of chain has been used, the weight of the material being lifted has caused damage to the cargo where the chain strand "bites" into the cargo. Additionally, the use of multiple strands of chain, necessary when greater weight is to be lifted, will result in a "bunching" of the chain strands when the cargo is lifted which can compound the bits and cause damage to cargo. On the other hand, if fabric, rubber or synthetic material slings are utilized they have the disadvantage of not being able to sustain the loads which chains can and also have an additional disadvantage of being easily cut which further weakens the sling. This in turn demands a complete replacement of the sling which is both costly and time consuming.